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Homework Help: Help with Stoichiometry

  1. Sep 27, 2005 #1
    a. A sample of CaCO3 decomposes when heated to form calcium oxide and carbon dioxide. 1.5432 g of CO2 are released in the reaction. Find g of CaCO3 in the original sample.
    CaCO3 --> CO2 + CaO

    1.5432 g CO2*(1 mol of CO2/44.01 g) = 0.035065 mol of CO2*(1 mol CaCO3/1 mol CO2) = 0.035065 mol CaCO3

    0.035065 mol CaCO3*(100.09 g/ 1mol CaCO3) = 3.5097 g CaCO3??

    b. The original sample was a mixture from which only CaCO3 released carbon dioxide. Calculate the percentage by mass of CaCO3 if original's sample mass was 5.768 g.

    Do I divide 3.5097 g CaCO3/5.768 g * 100 or must I subtract the grams of CO2 from the original sample's mass?

    Last edited: Sep 27, 2005
  2. jcsd
  3. Sep 28, 2005 #2
    Any volunteers?

    Thanks again.
  4. Sep 28, 2005 #3


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    Staff Emeritus
    Science Advisor
    Gold Member

    That's correct.

    This looks a little silly, but your first idea seems right.
  5. Sep 30, 2005 #4
    all seemed right: (3.5097/5.768)*100 should do it.
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